The present invention relates in general to a optic fiber payout test system and pertains more particularly to an optic fiber payout system simulating the payout of fiber at high speeds during laboratory testing. The optic fiber payout system of this invention is an improvement over the conventional fiber payout test apparatus. This device provides a means for testing the payout of fiber optic cable in a manner that simulates the high rate of speed and high accelerations encountered during free flight. This capability is important for the development of launched fiber optic guided weapons systems and in particular, air launched optic guided weapons systems.
Prior to the development of the present invention, the primary means for performing this type of optic fiber payout testing was via captive flight testing or free flight testing. These methods of flight testing tend to be very expensive. As previously stated, an apparatus was needed to produce a high acceleration fiber optic cable payout initiation in a laboratory environment. This invention would simulate the accelerations seen by fiber optic data links during air launches and other launches from various platforms. This invention would also allow different fiber payout designs to be tested in an inexpensive and simple manner.
The launch period is known to be critical for fiber payout systems. A laboratory based test apparatus or system that simulates such launch periods for fiber payout is preferred over launching weapons from an aircraft. This is primarily due to the repeatability of a laboratory test, the ability to collect reliable data as well as the capability to control various parameters that affect the fiber payout. In addition, a laboratory based test apparatus or system is easier to use and costs less than flying an aircraft for each test. The present invention also provides a quick and easy set up for other fiber pulling needs such as fast camera coverage of payout and test ancillary equipment such as fiber payout counters, strain gauges, and other sensors.
In many fiber payout systems the wire or optic fiber typically unwinds from spools, spindles or bobbins on either the launcher or the projectile or both. A major concern with many fiber payout systems is the reliability of the payout device during the launch period. Another drawback with many fiber payout system results from the extreme forces acting upon the wire or fiber as a result of the launch as the projectile accelerates away from the launcher. Yet another concern is the formation of a relatively long spiral helix and other such phenomena know as the ballooning of the fiber as it pays out. This ballooning effect creates an increase in the tensile loading on the wire or fiber as it continues to unwind. The tensile loads present during launch tend to fracture or break the wire or fiber thereby rendering the projectile ineffective.
Yet another problem often encountered is various fiber payout systems is the phenomena of macrobending and microbending of the optic fiber and corresponding disruptions or interference in the transported signals. However, as the operational speeds of these platforms and projectiles increase, the drawbacks associated with the ballooning effects, microbending and macrobending of the fiber, as well as the tensile loading become an ever increasing problem. Simulating such ballooning effects and initial forces in order to further study and develop solutions to the aforementioned problems encountered during the operational use of fiber payout systems is a task not adequately resolved by many existing laboratory based fiber payout test apparatus or systems.
Conventional laboratory based fiber payout test systems have been used for a wide range of testing applications simulating various platforms. They have been used for example to simulate shoulder launched projectiles, mobile mounted projectiles, land based launches, and by weapons dispatched by various aerial platforms. The conventional test apparatus or system typically pulls the fiber or wire with some sort of spinning wheel at high rates of speed. These machines normally take several seconds to ramp up to speed and are not capable of generating the high acceleration seen during operational launches. These typical payout test apparatus and systems also have the drawback that they do not accurately simulate the loading that occurs during high speed payout as discussed above. This present invention, on the other hand, provides a test apparatus or system which is capable of generating a high acceleration mode in a very short period of time and simulating the actual loading that occurs during high speed payout.